Ability of 17 strains of trichogramma to control Plutella xylostella l. (Lep.: Yponomeutidae), in the laboratory.

To set up a biological control method against Plutella xylostella, in cabba ge crops, the efficiency of 17 strains of Trichogramma and Trichogrammatoid ea were compared. Laboratory experiments were divided into 2 phases. The fi rst test was carried out in tubes containing P. xylostella eggs (or Ephesti a kuehniella eggs), and females of each Trichogramma strains. This test all owed a preliminary choice: among all the strains, only 10 were retained thr ough criteria of P. xylostella eggs parasiting ability. These species are T . voegelei, T. oleae, T dendrolimi, T. bactrae, T. exiguum, T. chilonis, T. pretiosum, T. buesi and T. ostriniae. The second test was carried out in c ages where P, xylostella eggs had been placed on a cabbage leaf. This exper iment introduced the "egg finding" factor and the "cabbage environment" fac tor. According to parasitism rates, T. oleae ranked first. Among all the st rains rested and according to the 2 laboratory experiments, T. oleae was th e most efficient Trichogramma species to control P. xylostella.